Koji Igarashi apologized to a packed house at the Game Developers Conference: He has to be careful about how he talks about the defining work of his career. That's because he's just left Konami, where his legacy in the "metroidvania" genre lives -- elusively, and like a father he referred to his defining work only as "S.O.N."

Symphony of the Night, an ornate, lavish gothic sprawl pitted and dotted with secrets and hidden jewels, unravels slowly: as a genre term, metroidvania refers to exploration through the use of a gradually-expanding toolset -- players explore and then double back once they learn to reach an area they couldn't before.

As an installment in the Castlevania franchise, SotN is especially significant for the elegant creative departures it made from prior installments in the gothic action franchise about whip-cracking vampire hunter.

His team was asked to make a game within the universe, but believed at the time they weren't "franchise owners" within the organization: "We figured we could do whatever we wanted, so long as we treated it as a separate series," he says.

The team was tasked with improving the game's controls and extending its lifespan, without meaningfully conflicting with the canonical brand. An early significant decision was to remove death by falling, a standard of the fairly grueling earlier Castlevania games ("we hated, hated falling to your death," he says).

Inspired by ways to iterate on systems presented by Zelda and Metroid, Igarashi implemented RPG-style experience points, and power-ups rather than just recovery items as rewards for boss fight, to increase the way that curve feels meaningful.

But for a game about exploration, the team needed to go further. They wanted to make the character slightly larger, and centered in the screen rather than scrolling from left to right, as the hero can no longer die from falling and should be encouraged to move in a nonlinear way.

"Due to being able to move the character in both left and right directions, we placed the character in the center," says IGA. But the iconic whip-cracking heroes of Castlevania created something of a space problem: The length of the weapon no longer suited this new visual paradigm.

Igarashi was challenged to come up with a new character without violating the rules of the established universe. But there are a lot of other characters in the canon, especially if you decide they don't have to be human. "A non-human can also clear the challenges of hidden maps, right?"

There's Dracula's son, of course, who could possibly strike a graceful, compelling figure. Yet "looking at the existing materials, there was a lot that didn't make sense: why would a vampire get close with humans, why would the character be at odds with his father?"

"The half-human factor isn't convincing enough to make him want to get close with humans," he reflected. "So I changed my perspective, and thought about this from another angle: If he's half human, that means one of his parents is human - we already knew that his father is a vampire, which means his mother is human, which then means that there was, in fact, love between a vampire and a human."

"But then, the next thing you know, the vampire is growing hostile toward humans and is now the devil," says Igarashi. "So... let me think about this while respecting the Dracula story. If there was love between a human and a vampire, would she be happy watching her own husband turn against the humans? And time frame wise, it overlaps with the witch hunts."

Castlevania's story had surprising depth for its time: The main character, Alucard, is a vampire who hid himself away from the world to avoid harming humans, in the wake of his mother's death in a witch hunt. He wakes up when his father resurrects, as he does once per century, and the vampire hunter who is ordained to face and defeat him goes missing. Inside the sprawling 2D gothic exploration game are themes about the lead character's relationship to his family and identity.

"All men have a mother complex," says Igarashi.

So the main character is half-vampire. The main characters in the previous games were sort of macho and have a rugged style, but the vampires have a strong but transient image. The gothic style really suits them. "So we thought, let's go ahead and change the art style, too. We contacted the publisher, got directly in touch with the illustrator, and negotiated the character more to our liking: So there you have it, a new look and a new gameplay style."

Igarashi's team made some logical decisions that led to the game's distinctive visual and environmental depth: lower resolutions, fewer colors but more palettes led to a higher rendering speed on and more images outputted at once on the PlayStation 1.

It needed a large map, and the player's desire for equipment would be the main element that drew them to explore that map. "Even though I say exploration, there is a limitation to how much exploration can be allowed," he says. "It depends on the game, but if the player were to simply clear the game, maps are created with a single path, with hardly any going back."

"If you were the type of player who wanted to move the story forward, revisiting a previous area can be a burden, but not if you were determined to unlock every little thing," he says. "Because of that, if the revisiting led to a dead end, we need to provide a reward in the form of an item, or something."

"Also it can be effective to guide the player along the main path by adding items to branches. It provides an atmosphere to the player, and at an early stage I try to provide moments where the player is unlocking new areas through the skills they have acquired."